The Chinese-language version of the website was reported to be fully accessible this week.

The press freedom group Reporters without Borders praised the bosses of Wikipedia, who they said had "always refused to go in for self-censorship".

Other internet giants have been criticised for censoring their services or complying with strict Chinese rules.

Wikipedia - which allows users to add to and edit the website's information - was becoming increasingly popular in China until it was blocked in late 2005.

China has strict laws on internet use and blocks content it deems a threat, including references to the Tiananmen Square massacre and notable dissidents.

It also blocks the BBC News website.

'Neutral view'

Critics say global internet firms such as Yahoo, Google and Microsoft have compromised their principles, justifying this by saying it was the only way to gain access to China's fast-growing market.

"The Wikipedia example proves the contrary," the Paris-based Reporters without Borders said.

"The Chinese government is pragmatic and does not want to do without foreign businesses in the internet sector. There is obviously room for negotiation for the US companies."

A Chinese-American former academic and Wikipedia specialist, Andrew Lih, reported the lifting of the block.

In his blog, he said he believed the Chinese authorities gave way because of Wikipedia's consistent argument that it "has a neutral point of view at its core, with no activist or subversive agenda to the site".

"In the end, I believe consensus among the authorities determined the benefits of Wikipedia far outweigh the risks."

There was no immediate official word from the Chinese authorities on the lifting of the block.